A new paper out of the Finland University of Kuopio associates the sugar mannose with possible prevention of cancers by inhibiting hyaluronan synthesis. High hyaluronan levels are associated with many human cancers. Hyaluronan (also called hyaluronic acid or hyaluronate) is a glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is one of the chief components of the extracellular matrix, contributes significantly to cell proliferation and migration, and may also be involved in the progression of some malignant tumors.

Mannose Inhibits Hyaluronan Synthesis by Down-regulation of the Cellular Pool of UDP-N-acetylhexosamines

From the Institute of Biomedicine/Anatomy and Department of Pharmaceutical Chemistry, University of Kuopio, P. O. Box 1627, FIN-70211 Kuopio, Finland

We found that D-mannose dose-dependently decreases hyaluronan synthesis in cultured epidermal keratinocytes to 50%, whereas glucose, galactose, and fructose up to 20 mM concentration had no effect. The full inhibition occurred within 3 h following introduction of mannose and did not involve down-regulation of hyaluronan synthase (Has1–3) mRNA. Following introduction of mannose, there was an 50% reduction in the cellular concentration of UDP-N-acetylhexosamines (UDP-HexNAc, i.e. UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine). On the other hand, 2 mM glucosamine in the culture medium increased UDP-HexNAc content, stimulated hyaluronan secretion, and negated the effect of mannose, supporting the notion that the inhibition by mannose on hyaluronan synthesis was because of down-regulated UDP-HexNAc content. The content of UDP-glucuronic acid, the other building block for hyaluronan synthesis, was not reduced by mannose but declined from 39 to 14% of controls by 0.2–1.0 mM 4-methylumbelliferone, another compound that inhibits hyaluronan synthesis. Applying 4-methylumbelliferone and mannose together produced the expected reductions in both UDP sugars but no additive reduction in hyaluronan production, indicating that the concentration of each substrate alone can limit hyaluronan synthesis. Mannose is a potentially useful tool in studies on hyaluronan-dependent cell functions, as demonstrated by reduced rates of keratinocyte proliferation and migration, functions known to depend on hyaluronan synthesis.

* This work was supported by Grants 107173 and 108484 from the Academy of Finland, by grants from Finnish Cancer Foundation and Sigrid Juselius Foundation, and by a research grant from Kuopio University Hospital. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. The on-line version of this article (available at http://www.jbc.org) contains supplemental Table S1.